Combine gingersnaps, sugar, and salt in a food processor, pulsing until fine crumbs form.
With the processor running, drizzle melted butter until crumbs start to come together.
Press the crumbs into a 9-inch pie pan, then bake at 350 F for 12 minutes. Let it cool on a wire rack.
Bloom gelatin in water, letting it sit for 5 minutes until soft.
Separate eggs, placing yolks in a bowl and whites in a stand mixer bowl.
Whisk yolks, 1/2 cup sugar, salt, spices until pale. Warm buttermilk and cream, then dissolve gelatin in the mixture.
Slowly pour the hot liquid into the yolk mixture, whisking to combine. Add pumpkin puree and set aside.
Whip egg whites until frothy, gradually adding remaining sugar. Continue until stiff peaks form.
Fold whipped egg whites into the pumpkin mixture, ensuring no streaks.
Pour the filling into the cooled pie shell and refrigerate for at least 4 hours or overnight.
Bloom gelatin, then dissolve in the microwave until liquid.
Beat cream until it begins to thicken, add sugar and vanilla, then slowly pour in the liquid gelatin while beating.
Spread stabilized whipped cream on top of the set pie.